Burner safety pilot apparatus



Nial'thrlo,v A lw PETERS t y BURNER SAFETY PILOT APPARATUS c0\ INVENTQR.

BY AlA/Peers' dir ,I

A. W. PETERS BURNER SAFETY PILOT APPARATUS March-1o, 1959 vssheets-sheet 2 mea- Jari. l11. i955 III OJ Mw Wd P m W. A M

March 10, 1959 A. wi PETERS BURNER SAFETY PILOT APPARATUS Filed Jan. l1.1955 3 Sheets-Sheet v3 j w, .W1 -wf\ /wm .w QN uw wv QN Ammw. Nrw ABM-WW m uw uw H 4Arthur' W. Peters, Toledo,

:for the front end 2,876,832 BURNER SAFETY PrLoT APPARATUS Ohio,assignor to Surface Comhustion Corporation, Toledo, Ohio, a corporationof "Ohi Application January 11, 1955, Serial No.481,127 4 Claims. (Cl.15S- 115) The present invention relates to va safety pilot for aheatingpunit comprising va burner which formsa closure of a cylindricalcombustion chamber wherein a whirling stream of air is utilized forsupporting combustion of the fuel issuing from the burner. The primaryobject of the invention is to provide a safety pilot which shall embodyimprovements in means for producing a pilot flame which may not vbereadily extinguished and which shall embody an improved thermal Velementfor shutting ofi the main fuel valve of the heat ing unit in case thepilot ame becomes extinguished. Other related objects will more fullyappear hereinafter. Fora consideration of what l believe to benovel andmy invention, attention is directed to the following portion of thespecification 'and the drawings and claims appended thereto. i

`In the accompanying drawings forming part of this specication,

Fig. l shows apparatus embodying the present inven tion. v

'Fig 2-is a fragmentary end elevation with a portion in section of theleft 'hand portion of the apparatus shown in Fig. l.

Fig. 3 is a section al view shown in Fig. 1.

Fig. 4 is a section on line 4 4 of Fig. v3.

Fig. 5 is a partial section on line 5*5 of Fig. 3.

Fig. 6 is a sectional view of a portion of the apparatus as shown inFig. 3 with modified piping for fuel supply.

Figure 7 is a wiring diagram for the apparatus.

In Fig. l, the front portion of a cylinder lwhchrequires to beinternally heated is indicated at 10, this cylinder defining thecombustion chamber of va heater wherein fiuid medium required to beheated is confined about the outer side of said cylinderby a surroundingjacket 11.

.A burner for internally heating the cylinder l is generally indicatedat 12, the burner having a peripheral flange 13 by which it isdetachably secured to a complemental fiange 14 on the heater. The burnercornprises a front wall l which forms a closure for the front end of thecombustion cylinder except for a central circular opening 16 whichconstitutes an inlet for combustion supporting air froma circularchamber 17 whose back wall is indicated at 20 and whose circumferentialside wall is indicated at 21. The chamber 17 has a `tangential air inlet22 so that a stream of air entering with :relatively high velocity will.whirl in said chamber and thus issue from the central opening 16 ofsaid chamber with a whirling motion. Air under pressure is con` ductedto the tangential inlet 22 by a supply pipe litt leading from a motordriven blower not shown. The burner also comprises a central fueldischarge nozzle 23 which extends through the airchamber 17 coaxial withthe central opening lo thereof. The fuel discharge noz- 21e 23 extendsfrom a hollow head 24 .to which vgas .is delivered by a supplypipe 25having a normally closed motor operated shut-off valve 2'6.lThelfuel.issuesfrom of a portion of the apparatus v axial with thecombustion chamber 36 at 'the nozzle 23 with `relatively low velocityand because the air from the opening 16 enters the combustion cylinderwith a whirling motion the fuel rapidly intermixes with the air, hencethe flame of combustion will also tend to whirl in 'said cylinder aswill now be readily The fuel thus delivered to the combustion 'cylinder10 understood. l

The fuel thus delivered to vthecombu'stion cylinder 10 is ignited by ailame issuingfrom a pilot combustion tube `V27, the tube extendingwithin the burner nozzle 23 to a point where the iiam'e issuing from thetube kwill serve to ignite the combustible mixture outside ofsaid'no'zzle. Because the pilot flame issues from said tube 27 with=`substantial velocity, the discharge end of said tube 27 may, terminatein relatively close proximity to the discharge end of the burner nozzle23. The pilot ame thus issuing from the outlet end of the pilotcombustion tube 27 is produced by a pilot burner head 28 mounted on thefront, or inlet end of, said tube, to the end that the said tube may beinternally heated for a reason presently appearing. The pilot combustiontube 27 is supported by a tubular support 34 through-'which it extendscoaxial with the burner nozzle 23 from beyond the end Wall 35 of thehollow head 2d from which said nozzle 23 extends, said tubular support34 being mounted on and extending from said wall 3S, The tubular'support34 and the pilot combustion tube 27 are rigidly interconnected at apoint remote from said end wall by :a weld 33, the tube being otherwisefreeto thermally expand and contract relative to said support for areason presently appearing.

The pilot burner-apparatus comprises wall means ttl and 41 forming acylindrical combustion chamber v36 in the pilot-burner head 2S. The endwall 41 is mounted on theinlet end of the pilot combustion tube 27. Astream of air under pressure is supplied tangentiall'y to the Walls d@of the combustion chamber through 'anim let 42 to which air underpressure'is delivered by a tangential supply pipe 43 so that the airthus entering said chamber 36 tends to Whirl therein. ln the burner head2S nozzle means `for deliveringl fuel gas to the cornbustion chamber 36forms a passage vor chamber' 44 c'oa gas discharge port in wall 40thereof through which port gas vis normally delivered into the axis ofthe combustion chamber 36. The passage or chamber 44 is amply large -toaccommodate the electrodes of spark plug means 5d mounted on the pilotburner structure and adapted to produce an ignition spark in the gaschamber or passage 44. The outer end of the passage 44 is 'closed by asight glass 45. A supply pipe d6 having its own shutoff valve 53, shownin Fig. l, forms gas conduit means kfor delivering fuel gas to the gaschamber it through a fitting having a gas metering orifice 47. The gasthus admitted to the gas inlet passage 44 requires to be admixed withair to be ignita'ble by the spark plug 5t). Airis delivered by airconduit means comprising. air supply pipe 51 through an air meteringoriice 52 in said fitting, this is preferably a relatively small modicumor stream of air compared to the stream of gas fed through orifice 47 tothe chamber "i4 and is normally insufficient to form an ignitablemixture therein when the valve 53 is vfully opened. To obtain such anignitable mixture, the gas valve 53 is turned closed or shut of and airis allowed to pass through the fitting and the chamber d4 to purge gastherefrom,l Thus lthe lair required to be admixed with the gas in thegas inlet passage or chamber 44 before the gas can be ignited by thespark plug 5t) is air already present in the passage and in theconnecting combustion chamber 36 at the time the shut-ott vaive 53 inthe gas pipe t6-is opened,l the air being present 'because the firstvstep in starting the heating apparatus lis ,to lstart the combustionlair blower which delivers air to the plug may thereafter main airsupply duct 18 and therefore also to the branchair pipes 43 and 51, atwhich time the gas valve 53 in the gas conduit 46 upstream of thefitting where the air conduit 5l joins said gas conduit is closedwherebyv the air may flush gas lfrom the chamber 44 as before described.The first surge of gas into the gas inlet passage or chamber 44 uponopening the gas valve 53 provides an air-gas mixture in the gas chamber44 for initially igniting the pilot burner, said mixture being readilyignited by the spark plug 50. Once ignited, the gas remains ignited inthe pilot combustion chamber 36 and therefore the spark be de-energized.By thus locating the electrodes of the spark plug in an ignition chamber44 separate from the combustion chamber 36 proper and in a passage whichduring normal operation of the pilot burner is purged with anunignitable gas, the electrodes do not become overheated and they do nottend to retard the whirling of the air in the pilot combusion chamber36.

In an alternate arrangement, the pilot burner, shown separately in Fig.6, is supplied vwith combustion air through the inlet 42 and with fuelgas through supply pipe 46 and the chamber 44. This differs from thearrangement in Fig. 3 only in that air is not supplied to the fuel gasinlet to the chamber 44. In this case, air from the tangential inlet 42is relied on to purge the chamber 44 before the fuel gas is turned on,and in other respects the operation is as described for Fig. 3.

In operation ofthe pilot burner l.ithas lbeen observed that initialignition takes place'without fail when the fuel gas initially mixes withresidual air'in the cham- Y safety pilot ber 44,'then the ame frontmovesv away from'the spark plug, through the combustion chamber 36, andby proper adjustment of fuel gas and combustion air streams, the llameignition front may be made to move .into the pilot combustion tube 27.Thus the electrodes of the spark plug are surrounded by a cold fuel gasatmosphere, and when the flame from the pilot burner has causedsufficient expansion in the tube 27 to actuate the switch 30, the sparkplug will be de-energized. The satisfactory operating life for thesespark plugs has been found to be 'beyond reasonable measure, and this isa distinct improvement in an art where fouling and electrodedeterioration are commonplace. Switch 30 is a Vcommercially availablelimit switch having a set of normally open contacts SP1 and a set ofnormally closed contacts .SP-2. When tube 27 is cold, the switch 30 isdepressed by adjustable actuator 32 carried on projection 19 of theburner generally indicated at 12, andv contacts SPfl are closed whilethe contacts SP-2 are open. Upon expansion of tube 27 due to heat fromthe pilot burner, the switch 30 moves away from the actuator 32, andcontacts SP-1 and SP-2 revert to their normal positions.

The control system for the burner safety pilot apparatus is shown indetail in Figure 7, as applied to a liquid heater wherein liquid to beheated is circulated to the space between walls 10 and 11 of Figure l bya liquid pump not shown.

A liquid pressure switch with a normally open contact PS is placed atAthe pump outlet.- A temperature limit switch having a contact TLS and atemperature control switch TS are placed in the liquid circuit to avoidoverheating the liquid, and to normally control the heater. Controlswitch 30 contains two safety pilot switch contacts SP-l and SP-2 in asingle pole, double throw fast operating switch so that they cannot bothbe closed at the same time.

When the liquid pump is started, pressure on the pres sure switch closescontact PS. Then the burner starting switch SW is closed. If the liquidis cold, i. e., 'below the high limit control temperature for TLS andalso 4 is below operating temperature, switch contact'SPl of switch 30will be closed and Vswitch contact SP-Z will be open. A spark relay coilSR will thus be energized and its contacts SR-l and SR-2 will close.

Closing of SR-l energizes a control relay coil CR, thus closing itscontacts CR-l and CR-2.

The closing of CR-l locks the control relay CR closed, and the closingof CR-2 starts the air fan motor FM for supplying combustion air to thepipe 18. When the fan motor FM is nearlyup to speed, an air pressureswitch AS closes, energizing the coil SVP of the pilot gas valve 53, andenergizing the spark plug 50 through a spark transformer ST.

As the gas is ignited and burned in the pilot burner, the tube 27expands and actuates the switch 30 to its hot position, opening contactSP-l to de-energize the spark relay coil SR and energize the main burnervalve coil SVB. This opens the main gas burner valve 26 and the mainburner starts to burn at full rate. Y

When the liquid is suciently heated to satisfy the temperature controlswitch, TLS opens, which in turn opens CR to close both gas valves 53and 26. No short interruption of electric service will allow valves 53and 26 to re-open because the holding circuit CR-l is broken and SP-l isheld open until the pilot tube 27 contracts by cooling suicient toactuate switch 30.

As will beappreciated by persons versed in the art, this control systemcan be altered slightly to provide a constant burning pilot by lmovingthe temperature control switch TS from its position as shown in Figure 7to-the circuit conduit connecting the main burner valve solenoid SVB, sothat upon satisfaction of the ternperature control system, the circuitto the relays SR and CR would not be broken; similarly, if a throttlingcontrol system is desired, then a suitable throttling control valve isplaced in the main gas line 25 of Figure l, and contact TS is eliminatedfrom Figure 7. A bulb controlled valve, with the temperature responsivebulb placed in the heated liquid circuit, is commonly used for this typeof control system.

From the foregoing description it is believed to be apparent that thepresent invention provides a safety pilot which is well adapted for itsintended purpose.

This application is a continuation-in-part of my ap plication Serial No.78,025, filed Feb. 17, 1949, now abandoned.

I claim:

l. Burner apparatus comprising, in combination, vwall means forming acylindrical combustion chamber and an inlet thereto for supplying astream of combustion supporting air to said chamber and causing said airto whirl in said chamber, a cylindrical gas nozzle extending into saidchamber along the axis thereof, a relatively long pilot combustion tubehaving an inlet end and an outlet end, said outlet end being disposedwithin said gas nozzle and adapted to discharge a ame through said gasnozzle for ignition of fuel gas issuing therefrom, a pilot burner headmounted on the inlet end of said tube for supplying below the normalcontrol temperature for TS, then the circuit is closed to the coil SR ofa spark frelay. If the flame to the tube for heating the latter andcausing thermal expansion thereof and for producing a flame at theoutlet end of said tube, an elongate support for supporting said tube ata lpoint remote from said head, a fuel gas valve for controlling flow offuel gas to said gas nozzle, and a control switch adapted to controlsaid valve responsive to relative movement of said tube and saidsupport.

2. In a safety control apparatus for a combustion unit having structuredefining a combustion chamber, the

combination which comprises a fuel supply valve, a 'Y conduit fordelivering fuel from the outlet of said valve to said chamber, a pilotcombustion tube having an inlet end and an outlet end, a pilot burnerhead mounted on. the inlet end of said tube for supplying flame tothetube for internally heating the latter and causing thermal expansionthereof and for producing a pilotV dame at the outlet end of said tube,said pilot burner head comprising a structure defining a cylindricalpilot combustion chamber having in its side a tangential inlet for airunder pressure so that the entering air tends to whirl therein andhaving at one end an axial fuel gas inlet in gas receiving connectionwith a source of gas supply so that the whirling body of air initiallytends to en velop the entering stream of fuel, a spark plug mounted onsaid pilot burner head for initially igniting the fuel gas entering saidpilot combustion chamber from said fuel gas inlet, said spark plughaving a spark gap disposed in said fuel gas inlet, a support forsupporting said tube with the inlet end of the tube in sufiicientlyclose proximity to the point of entry of the fuel to said chamber topermit said pilot ame to ignite said fuel, said pilot combustion tube ata point remote from its inlet end being fixedly secured to said supportso that between said point and its inlet end said tube may be free tothermally expand and contract relative to said support, and meansresponsive to said thermal expansion of said tube for closing said valvewhen said tube is relatively cold and for opening said valve when saidtube is relatively hot.

3. In a safety control apparatus for a combustion unit having structuredefining a combustion chamber, the combination which comprises: a fuelsupply valve; a conduit for delivering fuel from the outlet of saidvalve to said chamber; a pilot combustion tube having an inlet end andan outlet end; a pilot burner head mounted on the inlet end of said tubefor supplying flame to the tube for internally heating the latter andcausing thermal expansion thereof and for producing a pilot iiame at theoutlet end of said tube, said pilot burner head comprising a structuredefining a cylindrical pilot combustion chamber having in its side atangential inlet for air under pressure so that the entering air tendsto whirl therein and having at one end an axial fuel gas inlet in gasreceiving connection with a source of gas supply so that the whirlingbody of air initially tends to envelop the entering stream of fuel; aspark plug mounted on said pilot burner head for initially igniting thefuel gas entering said pilot combustion chamber from said fuel gasinlet, said spark plug having a spark gap disposed in said fuel gasinlet; a support for supporting said tube with the inlet end of the tubein sutiiciently close proximity to the point of entry of the fuel tosaid chamber to permit said pilot flame to ignite said fuel, said pilotcombustion tube at a point remote from its inlet end being fixedlysecured to said support so that between said point and its inlet, endsaid tube may be free to thermally expand and contract relative to saidsupport; and means responsive to said thermal expansion of said tube foractivating said spark plug when said tube is relatively cold and forde-activating said spark plug when said tube is relatively hot.

4. Burner apparatus comprising, in combination: wall means forming acylindrical combustion chamber and an inlet thereto for supplying astream of combustion supporting air to said chamber and causing said airto whirl in said chamber; a cylindrical gas nozzle extending into saidchamber along the axis thereof; a relatively long pilot combustion tubehaving an inlet end and an outlet end, said outlet end being disposedwithin said gas nozzle and adapted to discharge a flame through said gasnozzle for iginition of fuel gas issuing therefrom; a pilot burner headmounted on the inlet end of said tube for supplying tiame to the tubefor heating the latter and causing thermal expansion thereof and forproducing flame at the outlet end of said tube; an elongate support forsupporting said tube at a point remote from said head; a fuel gas valvefor controlling flow of fuel gas to said gas nozzle; a spark plug insaid pilot burner head; and a control switch adapted to activate saidspari:-

plug responsive to relative said support.

movement of said tube and References Cited in the le of this patentUNITED STATES PATENTS

